Non-Patent Document 1 discloses a vertical p-n diode in which a JTE (Junction Termination Extension) region formed in a termination region of the diode is separated into two regions by using two implantation doses.
The vertical p-n diode described in the Non-Patent Document 1 includes a vertical p-n junction structure made up of an n+-type SiC substrate, an n−-type drift region, a p+-type main junction, a cathode electrode and an anode electrode and a termination structure provided with a JTE region made up of a ring-shaped first JTE region (high concentration implantation region) and a ring-shaped second JTE region (low concentration implantation region) disposed on the surface of the n−-type drift region.
The first JTE region and the second JTE region described in the Non-Patent Document 1 are formed by multi-stage ion implantation of a p-type impurity such as Al, and the implantation dose ratio therebetween is 3 to 1. Further, though not described in the Non-Patent Document 1, according to the presentation at the meeting, the maximum implantation energy is 700 keV in both of the first JTE region and the second JTE region.
Non-Patent Document 2 discloses that an impurity concentration of a first JTE region is 2×1019 cm−3 and an impurity concentration of a second JTE region is 2×1018 cm−3 or 2×1017 cm−3.
Non-Patent Document 3 discloses that the spread in a depth direction in a concentration distribution of Al which is ion-implanted into SiC depends on an implantation energy.